CVE-2026-39383

Description

Gotenberg is an API-based document conversion tool. In version 8.29.1, an unauthenticated attacker with network access can force the server to make outbound HTTP POST requests to arbitrary internal or external destinations by supplying a crafted URL in the Gotenberg-Webhook-Url request header. The FilterDeadline function in filter.go is intended to gate outbound URLs, but when both the allow-list and deny-list are empty (the default configuration), it returns nil unconditionally and permits any URL. This is a blind SSRF: Gotenberg POSTs the converted document to the webhook URL and only checks whether the response status code is an error, but never returns the target's response body to the attacker. An attacker can use this to probe internal network infrastructure by observing whether the error callback is invoked, force POST requests against internal services that perform side effects, and confirm reachability of cloud metadata endpoints. The retryable HTTP client issues up to 4 automatic retries per request, amplifying each probe. This issue has been fixed in version 8.31.0. As a workaround, configure the GOTENBERG_API_WEBHOOK_ALLOW_LIST environment variable to restrict webhook URLs to known receivers, or set GOTENBERG_API_WEBHOOK_DENY_LIST to block RFC-1918 and link-local address ranges.

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CVSS v3.1 Score

7.2

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0007

Probability of exploitation

0.21%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-918 Server-Side Request Forgery (SSRF)

Affected Products

Vendor	Product	Versions
thecodingmachine	gotenberg	8.29.1 — 8.31.0

References

Advisories & Patches

https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5vh4-rgv7-p9g4 https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5vh4-rgv7-p9g4

Exploits

https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5vh4-rgv7-p9g4 https://github.com/gotenberg/gotenberg/security/advisories/GHSA-5vh4-rgv7-p9g4

Frequently Asked Questions

What is CVE-2026-39383? +

Gotenberg is an API-based document conversion tool. In version 8.29.1, an unauthenticated attacker with network access can force the server to make outbound HTTP POST requests to arbitrary internal or external destinations by supplying a crafted URL in the Gotenberg-Webhook-Url request header. The FilterDeadline function in filter.go is intended to gate outbound URLs, but when both the allow-list and deny-list are empty (the default configuration), it returns nil unconditionally and permits any URL. This is a blind SSRF: Gotenberg POSTs the converted document to the webhook URL and only checks whether the response status code is an error, but never returns the target's response body to the attacker. An attacker can use this to probe internal network infrastructure by observing whether the error callback is invoked, force POST requests against internal services that perform side effects, and confirm reachability of cloud metadata endpoints. The retryable HTTP client issues up to 4 automatic retries per request, amplifying each probe. This issue has been fixed in version 8.31.0. As a workaround, configure the GOTENBERG_API_WEBHOOK_ALLOW_LIST environment variable to restrict webhook URLs to known receivers, or set GOTENBERG_API_WEBHOOK_DENY_LIST to block RFC-1918 and link-local address ranges. It has a CVSS v3.1 base score of 7.2 (HIGH).

How severe is CVE-2026-39383? +

CVE-2026-39383 has a CVSS v3.1 score of 7.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0007, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-39383? +

CVE-2026-39383 affects products from thecodingmachine, specifically: gotenberg. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-39383? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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